up->irq was just duplicating up->port.irq so
delete the former and only use the latter.  We
were not initializing up->port.irq so this would
cause port shutdown crashes when synchronize_irq()
was called.

Based upon a bug report and patch from
RChan <rspchan@starhub.net.sg>
Signed-off-by: David S. Miller <davem@davemloft.net>